Carbonate-Suppressed Hydrothermal Synthesis of Tetragonal BaTiO3 Nanoparticles

Abstract

We demonstrate a carbonate-suppressed hydrothermal route for synthesizing tetragonal BaTiO3 (BT) nanoparticles using barium acetate as the Ba source. Commercial TiO2 (P25) was converted to BT in KOH at 240 °C for 6 h without post-annealing. Relative to conventional Ba(OH)2 routes, the acetate precursor markedly reduced BaCO3 formation and narrowed the particle-size distribution. Systematic tuning of the Ba/Ti ratio (≥ 1.3) further optimized nucleation and growth, yielding uniform ~100 nm particles at Ba/Ti = 1.7 with the highest tetragonality (c/a ≈ 1.0076), as verified by XRD (002/200 splitting) and corroborated by Raman signatures of the tetragonal phase. Trace carbonate, when present, could be removed by mild weak-acid washing (e.g., acetic or citric acid) as effectively as with strong acids, but with improved process safety and practicality. The combined use of barium acetate, controlled Ba/Ti chemistry, and gentle carbonate removal yields phase-pure, highly tetragonal BT nanoparticles from low-cost precursors in a short dwell time, offering a scalable pathway to MLCC-grade powders.